The aptly named big skate (Raja binoculata) is the largest skate in the waters off North America. Big skates range along the Pacific coast from Alaska to Baja California. They inhabit a variety of habitats, from bays and estuaries to the continental shelf. They prefer sandy or muddy bottoms and seem to prefer depths shallower than 390 ft. (120 m). They inhabit shallower water in the northern part of their range.
The largest big skate ever captured measured 7.9 ft. (2.4 m) in length, but they typically reach a maximum of 5.9 ft. (1.8 m) in length and weigh as much as 201 lbs. (91 kg). An average big skate weighs less than 110 lbs. (50 kg).
Dorsal Surface
A big skate has a diamond-shaped, flattened pectoral fin disk. It has a pointed snout, and the eyes are small and sit just ahead of the spiracles. The tail has two small dorsal fins but no anal fin, and the caudal fin is only a simple fold. A juvenile has smooth skin, but an adult’s skin has small prickles on the dorsal surface, the underside of the snout, between the gill slits, and on the abdominal region. An irregular row of approximately 33 middorsal thorns runs down the back and tail to the first dorsal fin. A single thorn protrudes from behind each eye. The back of a big skate ranges in color from mottled reddish-brown to olive-brown to grey, and it is covered with small, pale white spots or dark blotches. The ventral surface ranges from white to gray.
Ventral Surface
A large dark spot with pale borders appears on each wing of a big skate, and biologists suspect these “eyespots” appear to predators as the eyes of a much larger animal, making a shark or another predator much less likely to attack the skate.
A big skate camouflages itself by partially burying its body in the sand and silt on the seafloor. Between its submerged position and its mottled coloration, a skate appears nearly invisible to predators and prey. When partially buried, it breathes with the aid of the spiracles on the top of its body. It takes water in through these spiracles and pushes it out through the gills on its dorsal surface.
Big skates differ from Alaska skates in that their egg cases may contain as many as seven eggs each. The big skate produces the largest egg case of any skate species, measuring 9 to 12 inches (23-31 cm) long and 4 to 7 inches (11-19 cm) wide. Big skates have a maximum lifespan of 26 years, but most big skates in Alaska don’t live past 15.
Skates are mysterious creatures, and scientists still know little about them. We often catch skates when we sportfish for halibut. The angler usually thinks he has a halibut when the heavy fish hits the lure, but we soon know it’s a skate when the animal exerts long, steady pulls instead of the head-jerking motions of a halibut.
“What is it?” The angler asks when he reels the strange creature up to the side of the boat.
“It’s a skate,” I say.
“What’s a skate? Is it like a stingray?” He asks.
“It’s related,” I reply, “but skates and rays belong to different families.”
Skates in the family Rajidae differ from rays in the family Myliobatidae mainly because skates lay eggs, while rays give birth to live young. Both skates and rays are cartilaginous fish (they have no bones) and are related to sharks.
Biologists have identified 14 species of skates in Alaska, and eight of these species are considered common in the Gulf of Alaska and the Bering Sea. Two of the most abundant species in Kodiak Island’s waters are the Alaska Skate and the Big Skate.
The Alaska Skate ranges from the Gulf of Alaska to the Bering Sea and the Aleutian Islands and west to Japan. They live at depths from 56 to 1286 ft. (17-392 m) and prefer soft bottoms of sand, silt, or mud. They grow to 53 inches (135 cm) in length.
Alaska skates are long-lived and do not reach sexual maturity until they are ten years old. A female lays 20 to 40 eggs per year, and each egg is enclosed in a tough case to protect the embryo as it grows. Since a female skate has dual uteri and shell glands, she can form two single encased embryos at a time. The embryo grows for an average of 3.7 years before it emerges from its case as a fully developed young skate. In certain areas, skate egg cases litter the ocean floor, and beachcombers who find them on the shore call them mermaids’ purses or devils’ purses. Biologists have identified several skate nursery areas in Alaska’s waters. Some of these nursery areas have egg densities of over 100,000 eggs per square kilometer.
Alaska Skate Egg Case
A skate’s exceptionally long gestation period and its prolonged maturation until it can reproduce concern biologists. Skate populations are potentially fragile, and if targeted by commercial or sport fisheries, they could easily be overfished. Once considered a trash fish, skate wing is now presented as gourmet food in some regions. The Monterey Bay Aquarium lists skate as seafood to avoid because several North Atlantic species are now in decline from overfishing.
Juvenile Alaska skates eat mainly crustaceans such as amphipods and hermit crabs. As they grow, they begin to eat fish. While enclosed in their tough egg casing, skates remain protected from most predators, but hairy triton snails can prey upon a developing embryo by drilling through the case. Once they hatch, young skates are vulnerable to predation by any larger fish. Steller sea lions and other sea mammals sometimes feed on adult skates.
In my next post, I will profile the big skate, the largest species of skate in the waters off of North America.
The climate-change-induced temperature rise in the North Pacific Ocean has impacted flora and fauna from the tiniest phytoplankton to the largest whales. Since pre-industrial times, the oceans’ water temperature from the tropics to the poles has increased by 0.7°C. Scientists predict the water temperature will increase another 1.4°C to 5.8°C by the end of the century.
Melting sea ice and retreating glaciers offer the most visual evidence of these temperature changes, but our warming oceans’ impacts are many and varied. Most changes are subtle and occur slowly over time, but others explode into a mass mortality incident produced by something as seemingly innocent as a bloom of algae.
During the summer of 2015, warm weather across the North Pacific and West Coast of North America produced sea temperatures much higher than average. This warm water spawned massive algal blooms. While much of the algae was harmless, certain phytoplankton species in the bloom produced dangerous neurotoxins. Since plankton forms the base of the ocean’s food chain, this bloom negatively impacted marine life and fisheries from California to Alaska. Biologists identified nine dead fin whales near Kodiak Island in June and believed toxic algae caused their deaths.
During 2015, researchers noted extremely high levels of the algal toxin domoic acid, leading to closures of recreational razor clam harvests in Oregon and Washington. Fisheries managers also closed a large portion of the Washington state Dungeness crab fishery and some of the sardine and anchovy fisheries in California. Biologists measured the highest domoic acid levels ever recorded in Monterrey Bay, California, in May 2015.
Toxic algal blooms directly impact marine organisms, but ocean warming has also created many subtle changes to the biodiversity and population structures of organisms in the oceans, especially in the once ice-dominated areas of the northern Bering, Beaufort, and Chukchi Seas. Warming ocean waters have significantly affected gray whales in recent years. Increasing seawater temperatures in the Bering Sea have reduced winter ice cover in the region, which has led to a reduction in productivity. Primary productivity in the northern Bering Sea declined by 70 percent from 1988 to 2004. This previously ice-dominated, shallow ecosystem favoring large communities of benthic amphipods, the favorite food of gray whales, has been replaced by an ecosystem dominated by pelagic fish (i.e., those that dwell neither on the bottom nor on the surface). Gray whales have responded by migrating farther north, but biologists cannot predict what will happen if amphipod communities disappear from this region.
During the summer of 2018, the waters in the Bering Sea soared nine degrees Fahrenheit (5°C) warmer than average. Gray whales responded by migrating farther north to the Chukchi Sea. Still, amphipods might now be disappearing from this region as well, forcing gray whales to consume less nutritious krill, and krill might not contain the amount of fatty acids the whales need to build adequate blubber. By the spring of 2019, numerous reports noting gray whale carcasses washed up on beaches from Mexico to Canada were alarming whale biologists. By the end of that year, 214 dead gray whales had been sighted. Of these, 122 carcasses had landed on US beaches, 11 on the shores of Canada, and 81 on Mexico’s beaches. In the United States, 48 whales died in Alaska. Since most whales sink to the ocean floor when they die, the recovered carcasses probably represented only a fraction of the number of gray whales that died in 2019. Most of the whales died on their northward migration after a winter of fasting.
The warming ocean impacts the animals living in the sea and birds and animal that depends on the ocean for their food supply or any part of their life cycle. In Prince William Sound, surveys suggest the horned puffin population in that area declined 79% from 1972 to 1998. Biologists believe this decline in numbers is due to significant changes in the food base due to global warming. In the fall of 2016, hundreds of tufted puffins starved to death in the Pribilof Islands. Like the earlier deaths of horned puffins in Prince William Sound, researchers blamed their deaths on a shortage of food linked to higher-than-normal ocean temperatures in the Bering Sea.
In my recent posts on sharks, I noted that sharks have become more common in the North Pacific in the past decade. Pacific cod populations have crashed in recent years, and the numbers of halibut, pollock, crab, and salmon also seem to be on the decline. As the North Pacific warms, will other types of fish and invertebrates move in to fill the void left by the once-dominant species, or will the ocean become a toxic cesspool, lacking any life?
The reclusive, deep-dwelling Pacific sleeper shark (Somniosus pacificus) remains an enigma to biologists. Once believed to be sluggish bottom-dwellers that scavenged or fed on small fish and slow-moving prey, researchers now think Pacific sleeper sharks play a pivotal role in the North Pacific’s food web. Biologist Lee Hubert with the Alaska Department of Fish and Game studies Pacific sleepers, and he has learned the sharks spend little time on the bottom but instead move continually through all depths and are stealth predators of fast-moving prey.
I can understand how Pacific sleepers earned their reputation as sluggish sharks. We occasionally catch immature Pacific sleeper sharks when we halibut fish, and when reeled up to the boat, they look dead and move very little. I was surprised to hear these sharks are voracious predators. This shark’s ability to remain still, though, is one of the reasons it is such a successful predator. When it glides through the water, barely moving its body, it minimizes hydrodynamic noise, allowing it to elude acoustic detection by its prey.
Pacific sleeper sharks dive to depths exceeding 6500 ft. (1981 m). They typically remain deep during the day and then move to the surface at night, where they feed under cover of darkness. These sharks probably have poor eyesight, but they are extremely sensitive to electromagnetic fields. They can detect even minute electrical signals, such as the beating of an animal’s heart or its diaphragm’s movement. The shark does not need vision to detect these signals and attack its prey. Its dark grey body and stealth movements make it an efficient predator under the cloak of darkness.
The mouth of a Pacific sleeper shark is large and acts as a vacuum to inhale prey. Fish, such as salmon and cod, can be swallowed whole, but the shark uses its teeth to aid in eating larger prey items. Its upper jaw has small, sharp conical teeth used to hold the prey, while the teeth in the lower jaw interlock, forming a serrated blade used for slicing. A Pacific sleeper shark’s bite resembles the shape of a three-quarter moon.
Because they make little noise when traveling, a sleeper shark attacks with little warning. It might slowly swim up underneath a seal resting on the surface and attack the seal’s midsection, inflicting a fatal wound. Researchers know Pacific sleeper sharks eat fish, squid, octopuses, and marine mammals, but they are still trying to discern how much impact these sharks have on the their ecosystem. The number of Pacific sleeper sharks has increased dramatically in the North Pacific since the 1980s. Because they live very deep much of the time, it is difficult for biologists to estimate their population size. Still, in many areas where commercial fishermen caught few sleeper sharks in the 1970s, they now catch many.
Investigators are particularly interested to learn how many marine mammals Pacific sleeper sharks kill and eat. Pacific sleepers can grow to twenty feet (6.1 m) in length and weigh more than 8000 lbs. (3600 kg). They grow nearly as large as an adult orca, and recent evidence suggests these sharks might eat endangered Steller sea lions, especially sea lion pups.
In a 2014 study, biologists inserted “life-history transmitters” into the abdomens of 36 juvenile Steller sea lions.These transmitters record temperature, light, and other properties during the sea lions’ lives. When a sea lion dies, the tags either float to the surface or fall out onshore and transmit the data by satellite to researchers. After 17 of the original 36 tagged sea lions died, researchers noted that 15 of the transmitters indicated that predators killed the sea lions. Usually, when a predator kills a sea lion, the tag is ripped from the body and floats to the surface, recording a rapid temperature change and exposure to light. Three of the transmitters relayed data that suggested a very different type of predator, though. They recorded an abrupt drop in temperature, but they did not float to the surface and sense light, indicating that tissue surrounded them. The apparent explanation is that a cold-blooded animal, such as a shark, had eaten them. Other than sleeper sharks, great white and salmon sharks are the only other candidates living in the area near where the sea lions died. But both great white sharks and salmon sharks have counter-current heat exchangers in their bodies, giving them higher body temperatures than those recorded. Biologists think a Pacific sleeper shark is the only predator in the area that is large enough to eat a sea lion and has a body temperature as low as those recorded.
Pacific sleeper sharks live in polar and sub-polar regions year-round. They range from Baja California north to the Bering, Chukchi, and Beaufort Seas and the Okhotsk Sea off Japan. Biologists know little about Pacific sleeper shark reproduction and only recently learned they give birth to live young. Their social structure is also unknown, but researchers have photographed them feeding together in large numbers on whale carcasses.
Pacific sleeper sharks probably have a lifespan of more than forty years. Their tissue is toxic to humans and believed to be toxic to many other animals, so they have few natural predators except perhaps for other sharks.
I am always thrilled when I see the dorsal fin of a salmon shark protruding from the water as it swims near the surface. I love seeing any apex predator, but sharks conjure an air of mystery and fear. I wonder if the shark is chasing prey or if it is just watching and waiting for a fish to make the fatal mistake of swimming into its strike range.
Salmon sharks (Lamna ditropis) are some of the fastest fish in the ocean, and their high metabolism makes them voracious eaters. Salmon sharks are closely related to great white sharks, makos, and porbeagle sharks. Because their body shape so closely resembles a great white shark’s shape, people sometimes mistake salmon sharks as juvenile great whites.
Like other species of lamnids, salmon sharks have a conical snout, dark, round eyes, and a keeled, lunate tail. The salmon shark and porbeagle shark can be distinguished from great whites and makos by their smaller secondary caudal keel below the primary keel at the base of the tail. While the porbeagle shark inhabits the Atlantic and Southern Pacific, the salmon shark lives in the North Pacific.
A salmon shark has a bluish-black to dusky gray back, fading to white on the stomach. It has long gill slits and large teeth. Salmon sharks can grow to over 10 ft. (3 m) in length, but they average 6.5 to 8 ft. (1.9 – 2.4 m). They can weigh more than 660 lbs. (300 kg). Females grow larger than males.
Like other lamnid sharks, salmon sharks manage to sustain elevated body temperatures, even in the cold North Pacific. Their core body temperature measures approximately 80°F (26.7°C). They maintain this warm body temperature because they have a counter-current heat exchanger of blood vessels, directing heated blood through their core and dark musculature. This elevated body temperature permits the shark to live and hunt in a wide range of depths and water temperatures. The warm blood flow allows their brain, eyes, and muscles to function at peak performance.
A salmon shark is a big marine animal with no fur or blubber to keep it warm. To maintain its body heat, it must consume a large amount of food each day. Like a great white shark or a mako, a salmon shark aggressively chases its prey and sometimes even explosively breaches out of the water while in pursuit. Salmon sharks feed on fish, squid, other sharks, seals, sea otters, and marine birds. A study done in 1998 determined that salmon sharks consumed twelve to twenty-five percent of the total annual run of Pacific salmon in Prince William Sound.
While salmon sharks are most abundant in the North Pacific Ocean near Alaska, they travel as far south as northern Mexico and the Hawaiian Islands. Researchers have recorded salmon sharks dives as deep as 2192 ft. (668 m). Although biologists do not entirely understand salmon shark migrations, they believe the sharks spend the summer in the northern part of their range, and then they migrate south to breed. In the western North Pacific, salmon sharks migrate to Japanese waters to breed, and in the eastern North Pacific, they migrate south to the Oregon and California coasts. Their migrations are complicated, though, and they segregate by size and sex. Their migrations also depend upon available prey species in various areas. Scientists have determined that although many salmon sharks migrate south in the winter, some remain in the Gulf of Alaska and Prince William Sound year-round.
Male salmon sharks mature at five years of age, while females do not reach sexual maturity until they are eight to ten years old. They breed in the late summer or early autumn. Embryos develop inside their mother for nine months until she gives birth to between two to five pups. The developing embryos consume any unfertilized eggs in the womb. The mother provides no parental care to her young after birth, and they must fend for themselves. Females usually produce a litter every two years.
Male salmon sharks have a maximum lifespan of 25 years, while females can live 17 years. Other sharks sometimes eat salmon sharks, but humans pose the biggest threat. In Alaska, no commercial fishery exists for salmon sharks, but some sport fishing companies specialize in shark charters. Salmon sharks are big, strong, aggressive fish, and they pose a challenge and thrill for sport anglers. Each angler is limited to two salmon sharks per year. Salmon shark meat reportedly tastes similar to swordfish.
In my next post, I’ll describe another species of shark common in Alaska. Pacific sleeper sharks were long ignored as large, sluggish fish, but research over the past few years suggests Pacific sleeper sharks might play an essential role in the North Pacific’s food chain.
One of the most abundant sharks globally, Pacific spiny dogfish belongs to the family Squalidae (the dogfish family). Pacific spiny dogfish range from the Bering Sea to Baja California to Japan and the Korean Peninsula. They are most common off the west coast of the U.S. and British Columbia. Dogfish are typically bottom dwellers and inhabit depths from shallow coastal waters to 4,055 ft. (1,236 m). They prefer water temperatures ranging from 44.6° F to 59° F (7-15° C).
Pacific spiny dogfish are small, streamlined sharks. Males can grow to 3.3 ft. (1 m), while females measure a maximum length of 4 ft. (1.2 m). A dogfish has a distinctive snout, large eyes, and a flattened head. The body has a cylindrical shape. The top half is dark gray with scattered white spots, and this color fades to light gray or white on the underneath side of the fish. The teeth of a dogfish have sharp edges, but they are specialized for grinding instead of tearing. Dermal denticles comprise the scales of a dogfish. These denticles are the same rigid material found in their teeth, and they make the skin very tough.
A dogfish does not have an anal fin, but it has two dorsal fins, with a spine in front of each fin. These spines are venomous, and the shark uses them as protection against potential predators, such as other sharks or humans. The dogfish employs its two dorsal fins in different ways. The first dorsal fin helps it maintain stability while swimming, and the second dorsal fin provides thrust. The large caudal fin (or tail) allows the shark to maneuver quickly and efficiently through the water.
A dogfish has five gills on either side of its body, but unlike bony fish, a dogfish does not have gill covers. To breathe through these gills, the shark must remain in constant motion, so it either must continually swim or rest in a current where water rushes past its gills. A dogfish has an adaptation called spiracles, aiding it to breathe in calm water. These specialized gills, located behind the eyes, allow the shark to breathe when resting or eating.
Dogfish earned their common name from fishermen who observed them hunting in packs like dogs. Schools of hundreds of dogfish swim close together during the day, hunting herring, capelin, other small fish, squid, octopus, and even jellyfish. The dogfish uses its teeth and not its spines when feeding. It uses its spines for protection. Scientists think dogfish eat less in the winter when they migrate to great depths. They are preyed upon by larger sharks, seals, orcas, and some larger fish.
Spiny dogfish can live 100 years, and females do not reach sexual maturity until they are approximately 35 years old. Males can reproduce at an average age of 19. Males internally fertilize females in October or November. Dogfish are ovoviviparous, meaning females give birth to live young, and they have a gestation of nearly 24 months, the longest of any vertebrate. They give birth to up to 22 pups, and the newborns range in length from 8 ½ to 12 inches (21.6 – 30.5 cm).
Pacific spiny dogfish stocks remain stable and are carefully managed. In some areas of the world, a commercial market exists for dogfish, and they are considered a good food fish, but they are not yet in demand as a food source in the United States.
We usually catch a few dogfish each year during our sportfishing trips, but this past summer, we landed as many as 20 per day while halibut fishing. Dogfish are tricky to release because while you try to get the hook out of its mouth, the shark attempts to whip its body into a position to stab you with one of its venomous spines. I was not pleased to encounter so many dogfish this past summer, but more importantly, I wondered why we were catching so many dogfish. I speculate that the dramatic decrease in the Pacific cod population led to an increase in small fish species typically eaten by cod. Dogfish probably are exploiting an opening in the food chain. Will their presence affect the abundance of other fish species in this region of the North Pacific? Only time will tell.
Happy holidays, and I wish us all a nicer, brighter 2021!
Our guests are often surprised to learn sharks feed and swim in the frigid North Pacific. We catch spiny dogfish sharks when halibut fishing, and large salmon sharks terrorize commercial salmon gillnetters by ripping enormous holes in their nets when stealing fish from the mesh. Pacific sleeper sharks also live in Alaska’s waters, but sleeper sharks remain elusive, and biologists do not know much about their biology, diet, and habits. These three species fascinate me, and I think you will enjoy learning about their longevity, reproductive biology, and the mechanisms each species employs to stay warm in the frigid waters surrounding Alaska. I will cover each shark in detail in future posts, but for now, let me give you an overview of sharks in Alaska.
The three shark species I listed above are the most common but not the only sharks trolling the North Pacific. Over the past several years, ocean waters in the region have warmed, encouraging other shark species to venture into these nutrient-rich areas. Great white sharks began exploring Alaska in the 1970s, but recent, more frequent sightings suggest an increasing number of great whites have discovered the North Pacific’s fertile feeding grounds. Most of these visiting sharks only stay during the warm summer months, but researchers believe a small percentage find enough to eat to keep them in Alaska year-round.
Great whites are related to salmon sharks. Like salmon sharks, great whites have a highly developed countercurrent heat exchange mechanism that allows them to maintain a body temperature several degrees warmer than the ambient temperature. Sharks in this family represent some of the few species of endothermic fish in the ocean. Unlike their cold-blooded cousins, great whites and salmon sharks can produce bursts of speed to chase down prey, even in frigid ocean temperatures.
In recent years, Alaskans living and working in the far north regions of the Bering Strait and the Chukchi and Beaufort Seas have reported sightings of marine mammals with unusual wounds. Researchers noted that several ice-associated seals and Steller sea lions in the area suffered injuries from an uncommon predator.
Reports of seals with amputated flippers alerted biologists because killer whales have pegged teeth and don’t cause a slicing-type laceration. In some instances, scientists noted penetrating stab wounds and circular bite marks. Flesh torn by sharp, triangular teeth convinced researchers they were looking at the bite marks of a very large shark. Are the warming water temperatures and melting sea ice inducing great white sharks to travel further north where they can find a bounty of sea mammals to eat?
When great white sharks reach adulthood and grow very large, they seem to prefer eating marine mammals over fish, probably because marine mammals have a high energy-rich fat content. Observers have watched great whiles kill beluga whales in Cook Inlet, and biologists suspect they may even take walruses in the Bering Sea and the Arctic Ocean. Are great whites, at least in part, responsible for the diminishing numbers of Beluga whales? If the number of great whites increases in Alaska, will they affect other marine mammals’ population densities? Much more research is needed to answer these questions.
I’ll take a closer look at my nemesis, the spiny dogfish shark, in my next post. We used to catch one or two of these nasty little critters a year during our summer fishing trips, but we caught as many as twenty per day this past summer. Is this increase in spiny dogfish a trend, or was this past year only an anomaly?
What is “normal” these days? To me, “normal” feels like a train wreck occurring in front of me. I stand helpless, my eyes glued to the track while I watch the two engines barrel toward each other, brakes screaming. Chaos abounds in our government, our healthcare, our citizenry, and everywhere in our daily lives.
I attempted to watch the first U.S. presidential debate, but I had to turn off the television after only a few minutes. These are the people who are supposed to lead us out of the darkness. They are the ones who should formulate a comprehensive response to this pandemic to lessen its impact both physically and economically. Instead, they fought like children for ninety minutes, leaving me, and I’m sure many others, bewildered, confused, and frightened. Will our country survive this dark time in our history?
I am lucky to live in the wilderness, and I haven’t been to town since early March, so I’ve missed day-to-day issues of masks and social distancing. Instead, I’ve watched from afar, moving from fascinated to concerned to alarmed.
My selfish new normal might mean no vacation this winter, and I don’t mind. This summer, my husband, Mike, finished building my office/workshop, and I love it. It is a great place to write and research new ideas for posts and newsletters. Mike even enclosed a small, closet-like space and sound-proofed it to make me a podcast studio. This is the video of my she-shed, as we laughingly call it. https://vimeo.com/426004653.
Many of our guests canceled their reservations this summer, and most have rebooked for next year or the following year. Losing half of our season was tough, but I spent the extra time to work on my Kodiak wildlife book. I found an excellent editor, and we labored over every detail of formatting, sentence structure, and clarity. I knew editing this book would require a great deal of work, and it did, but I now have a clean manuscript. Next, I will work on photo placement, and then I will put the project on a thumb drive and mail it to my publisher. I hope to have the published book by early 2021. I am excited!
I’ve spent too much time watching the news this year, and of course, the pandemic and political climate have provided much fodder for future novel plots. Unfortunately, though, this new normal has distracted my creativity, and I’ve struggled to keep up with my writing schedule. In late November, once we close our lodge for the year, I hope to focus and increase my productivity.
I plan to write blog posts about a few more marine invertebrates, including sea cucumbers, urchins, clams, and mussels. Many of my posts originate from questions our guests ask me. When I can’t fully answer a question, I decide to research the organism and write about it. This summer, we caught several skates and way too many dogfish sharks. You will soon see a post about both skates and dogfish. I am especially curious about the dogfish and wonder what hole in the marine community they have rushed in to fill. Was this year an anomaly or the beginning of a worrisome trend? Unfortunately, the environment is also skewing toward a new normal.
A COVID vaccine might not return us to what we once considered normal, and I hope it doesn’t. I want to think we will emerge from this crisis wiser and kinder, but what I see now does not paint an optimistic portrait. If we do return to our old normal, I hope, at least, we will not take it for granted. If nothing else, we should learn that it only takes a tiny virus to destroy normal.
While Covid-19 is a novel virus, pandemics are nothing new in human history. In my last post, I wrote about the plague, and in this post, I’ll cover some of the other major pathogens that have not only inflicted disease upon humans but have caused pandemics affecting much of the globe.
Smallpox
Smallpox
For centuries, smallpox threatened Europe, Asia, and Arabia, killing three out of every ten people it infected. While smallpox menaced the old world for millennia, humans did not experience its full fury until European explorers introduced it to the New World. The indigenous inhabitants of Mexico and the United States had no immunity to smallpox, and tens of millions died. Anthropologists estimate smallpox decimated 90 to 95 percent of the indigenous population of the Americas.
The variola virus causes smallpox, and it is the only infectious disease humans have eradicated. Once they had a vaccine for smallpox, World Health Organization workers searched the most remote areas of the world, tracking down and vaccinating infected individuals and their contacts. The last natural case of smallpox occurred in Somalia in 1977. Unlike most viruses, smallpox only infects humans. No other species play host to the virus. Once all humans were vaccinated against smallpox, the virus had no place to go. Most human viruses can also infect other animals or insects, making these viruses impossible to find and demolish.
Cholera
Vibrio cholerae
Cholera is an infection caused by strains of the bacterium Vibrio cholerae, which attack the small intestine, causing watery diarrhea, vomiting, and muscle cramps. Cholera has wreaked havoc over the centuries and is the scourge of developing countries. Cholera is often spread through dirty drinking water, and it still kills nearly 30,000 people a year worldwide.
In the 19th century, cholera ravaged England and killed tens of thousands of people. No one understood how the disease spread until a doctor named John Snow linked the illness to a Broad Street pump in London, where many of the citizens obtained their drinking water. While cholera is no longer a problem in stable nations, it still lurks in developing countries that lack adequate sewage treatment and access to clean water.
AIDS
The human immunodeficiency virus (HIV) causes AIDS. Experts believe the virus originated in chimpanzees and began infecting humans in West Africa in the 1920s. AIDS became a pandemic in the late 20th century, killing an estimated 35 million individuals. Sixty-four percent of the estimated forty million people worldwide infected with HIV live in sub-Saharan Africa. Medication can now control HIV, and most HIV-infected individuals with access to the medication can live an average lifespan.
In my next post, I’ll cover the flu, an illness we all know well and carelessly dismiss as a minor inconvenience. Influenza has caused terrible pandemics in our past, and the flu virus keeps epidemiologists awake at night. These experts will tell you, “It’s not a question of ‘if’ we will have another flu pandemic but of ‘when’ the next flu pandemic will occur.
We find ourselves in the middle of a pandemic, but how dangerous is Covid-19? Should we stay at home? Do we need to wear masks? We listen to the biologists and politicians debate, and we weigh what they tell us. I think when trying to see the future, though, we must first turn around and look at the past. What cautionary tales does history provide us about plagues and pandemics? Let’s investigate the worst epidemics humans have endured, and maybe we’ll understand why we should take Covid-19 seriously.
I’ve thought and read a great deal about pandemics lately (hmmm, I wonder why?). What did we learn from the great influenza pandemic of 1918, or how did humans respond to the bubonic plague or smallpox?
Over my next three posts, I plan to discuss the worst plagues and pandemics the world has faced. Only one of the deadliest diseases ever to attack humans has been cured. Several of the others can now be treated, but a few infectious diseases remain elusive to us, even today with our advancements in science and medicine.
Let me begin with a plague I’m sure many of you think only belongs in the history books.
Yersinia pestis
The bacterium Yersinia pestis caused three of the deadliest pandemics in recorded history. This organism spawns the bubonic plague, septicemic plague, and pneumonic plague. The bacterium invades but does not harm fleas, and the fleas usually pass it on to small animals such as rats. Humans contract the plague either through flea bites or from exposure to the body fluids of dead animals infected with the bacteria. One to seven days after exposure to Yersinia pestis, a human develops flu-like symptoms, including fever, headaches, and vomiting. In the area where the bacteria entered the skin, painful lymph nodes swell and sometimes even break open. The plague poses a mortality rate of 30-90% if not treated. After the discovery and widespread use of penicillin in the 1940s, the death rate from the plague dropped to 10%.
The following represent three of the worst plague pandemics.
The Plague of Justinian
The Plague of Justinian hit Constantinople, the capital of the Byzantine Empire, in 541 CE. Historians believe the plague crossed the Mediterranean Sea from Egypt, brought by fleas carried on rats hiding in the grain holds of ships. The plague wiped out 40 % of the population of Constantinople and then raced across Europe, Asia, North Africa, and Arabia. In one year, this plague killed an estimated 30 to 50 million people or half the world’s population.
The Black Death
From 1346 to 1353, the Black Death annihilated between 75 to 200 million people in Europe, Africa, and Asia. Between 25% to 60 % of the population of Europe died during this pandemic. Experts believe this outbreak began in Asia and again jumped continents, spread by fleas riding on rats aboard merchant ships. People referred to the plague as the black death because of the black skin spots associated with the disease.
Humans did not know what caused the plague nor how to stop the disease, but they understood it spread by proximity to infected individuals. In Venice, authorities required boats to remain isolated and away from port for forty days to ensure the sailors did not bring the disease to shore. The Italian sailors referred to this forty-day isolation as “quarantino,” from which we derived the word quarantine.
The Great Plague of London
From 1348 to 1665, the plague continued to ravage England. The Great Plague of 1665 was the last and one of the worst of the epidemics, killing 100,000 London residents in six months. The name “Bubonic” derived from the appearance of blackened swellings, or buboes, in the victim’s groin or armpits.
While some reports state that Yersinia pestis is now extinct and no longer a threat, nothing could be further from the truth. In 2007, a wildlife biologist working in the Grand Canyon found a dead mountain lion. Curious about what killed the lion, he performed a necropsy on the animal. A week later, the biologist died. Yersinia pestis had infected both the mountain lion and the biologist. This death was not an isolated incident. Since 2000, the CDC has received between one and 17 reports per year of cases of the plague. Luckily, today we know to treat the plague with antibiotics, and this treatment not only helps stop the spread of the dreaded disease but also usually saves those individuals infected with it. Should Yersinia pestis become resistant to modern-day antibiotics, though, we could again face an epidemic of the plague.
In my next post, I’ll discuss smallpox, cholera, and AIDS. Until then, wear a mask, social distance, and wash your hands. From the Middle Ages to today, doctors have learned those are the only three sure actions humans can take to battle a pandemic.
